The present invention relates generally to devices and methods for generating electrons from diamond-like carbon material. Accordingly, the present application involves the fields of physics, chemistry, electricity, and material science.
Thermionic and field emission devices are well known and used in a variety of applications, such as cathode ray tubes, and field emission displays. Generally, thermionic electron emission devices operate by ejecting hot electrons over a potential barrier, while field emission devices operate by causing electrons to tunnel through a barrier. Examples of specific devices include those disclosed in U.S. Pat. Nos. 6,229,083, 6,204,595, 6,103,298, 6,064,137, 6,055,815, 6,039,471, 5,994,638, 5,984,752, 5,981,071, 5,874,039, 5,777,427, 5,722,242, 5,713,775, 5,712,488, 5,675,972, and 5,562,781, each of which is incorporated herein by reference.
Although basically successful in many applications, thermionic devices have been less successful than field emission devices, as field emission devices generally achieve a higher current output. Despite this key advantage, most field emission devices suffer from a variety of other shortcomings that limit their potential uses, including materials limitations, versatility limitations, cost effectiveness, lifespan limitations, and efficiency limitations, among others.
A variety of different materials have been used in field emitters in an effort to remedy the above-recited shortcomings, and to achieve higher current outputs using lower energy inputs. One material that has recently become of significant interest for its physical properties is diamond. Specifically, diamond has a negative electron affinity (NEA) that allows electrons held in its orbitals to be shaken therefrom with minimal energy input. However, diamond also has a high band gap that makes it an insulator and prevents electrons from moving through, or out of it. A number of attempts have been made to modify or lower the band gap, such as doping the diamond with a variety of dopants, and forming it into certain geometrical configurations. While such attempts have achieved moderate success, a number of limitations on performance, efficiency, and cost, still exist. Therefore, the possible applications for field emitters remain limited to small scale low current output applications.
As such, materials capable of achieving high current outputs in a vacuum by absorbing relatively low amounts of energy from an energy source continue to be sought through ongoing research and development efforts.
Accordingly, the present invention provides an amorphous diamond material that presents a combination of material and geometric aspects that allow the generation of electrons in a vacuum upon absorption of sufficient amounts of energy. Particularly, such a material includes at least about 90% carbon atoms with at least about 30% of such carbon atoms bonded in distorted tetrahedral coordination. The material is further configured with an electron emission surface having an asperity height of from about 100 to about 10,000 nanometers. In one aspect, the amount of carbon atoms bonded in distorted tetrahedral coordination may be at least about 50%.
The asperity of the emission surface may take a variety of configurations. However, in one aspect of the invention, the asperity has a height of about 10,000 nanometers. In another aspect, the asperity height may be about 1,000 nanometers. In addition to the height parameters, the asperity may also be configured with certain peak density parameters. In one aspect the asperity may have a peak density of greater than about 1 million peaks per square centimeter of emission surface. In another aspect, the asperity may have a peak density of greater than about 100 million peaks per square centimeter of emission surface.
A variety of energy types may be harnessed by the material of the present invention to facilitate electron flow therefrom, such as thermal energy, photonic energy, electric field energy, and combinations thereof. However, in one aspect, the energy may be thermal energy used by itself or in combination with electric field energy. In another aspect, the energy may be photonic (i.e. light energy), used either by itself, or in combination with electric field energy. In yet another aspect, the energy may be electric field energy.
A wide variety of energy intensities may be used as required in order to generate a desired electrical current with the material of the present invention. Such intensities may be determined in part, by the actual composition of the specific material used, the asperity of the emission surface thereof, and the type of energy input being used. However, in one aspect, the energy may be thermal energy that has a temperature of less than about 500xc2x0 C.
The amorphous diamond material of the present invention may be further coupled to, or associated with, a number of different peripheral components in order to for various devices that benefit from the material""s ability to generate electrons in a vacuum. For example, in one aspect, the amorphous diamond material recited herein may be incorporated into a device for emitting electrons that further includes an electrode coupled to the amorphous diamond material to form a cathode, and an anode positioned opposite the emission surface of the amorphous diamond material and separated therefrom by a vacuum space, into which the electrons are emitted upon input of a sufficient amount of energy.
Other components may be added as required in order to achieve a specific device. In one aspect, the electron emitting device may further include a gate positioned in the vacuum space between the emission surface and the anode, said gate being capable of creating an electric field when an electrical current is applied thereto. In another aspect, the gate may be a metal screen. In yet another aspect, the vacuum space may contain an amount of low energy cations that is sufficient to minimize repulsion forces between electrons emitted from the electron emission surface. Examples of suitable cations include without limitation, Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, and mixtures thereof. However, in one aspect, the cation may be Cs.
Those of ordinary skill in the art will readily recognize the potential for use of the present material in a wide range of devices and applications. Examples of such devices include without limitation, large and small scale electrical generators, cooling devices, transistors, switches, amplifiers, cathodes, electrodes, and ring laser gyroscopes among others. However, in one aspect, the device may be an electrical generator. In another aspect, the device may be a cooling device. In yet another aspect, such a cooling device may be capable of cooling an adjacent area to a temperature below about 100xc2x0 C.
The diamond material of the present invention may be made using a variety of techniques known to those skilled in the art. Such methods generally require a carbon source to be provided, and the formation of the amorphous diamond material using a deposition technique. However, in one aspect, the amorphous diamond material may be formed using a cathodic arc technique.
There has thus been outlined, rather broadly, the more important features of the invention so that the detailed description thereof that follows may be better understood, and so that the present contribution to the art may be better appreciated. Other features of the present invention will become clearer from the following detailed description of the invention, taken with the accompanying drawings and claims, or may be learned by the practice of the invention.